She is the homeroom teacher of Hazumu's class who has an excessively cute style shown through her loud expressions of love towards Hitoshi Sora or her passion for protecting her students in her class. Also, she is extremely clumsy which gives rise to her being the butt of many jokes.

Hazumu was a shy boy who enjoyed gardening, collecting herbs, and long walks in the mountains. One day he finally worked up the courage to confess his love to Yasuna, but she rejected him. 
Depressed, he wandered up Mt. Kashimayama, the place where they first met, to reconsider his feelings. After getting lost, he wished upon a shooting star and received a bizarre twist of fate. 
Now he is a she, and she stumbles headfirst back into social life and relationships only to find that the entire landscape has changed! 
(Source: Media Blasters)

[Wiki (jp)](https://ja.wikipedia.org/wiki/水谷優子)

Wife of [Mizuho Nishikubo](https://anilist.co/staff/102460/).

Passed away due to breast cancer on May 17, 2016.

Unaired 13th episode. 
Christmas has arrived on Earth and the story takes place 4 months after the event. Everyone starts to ready for Christmas and the love that will take place. Even the Aliens come and visit. When Yasuna tells Hazumu that she wants to go and walk by herself, Hazumu goes and tells Tomari. Hazumu waits for Tomari to accept her. (Source: Anime News Network)

Being a girl is harder than it looks... 
For Hazumu, this couldn't be truer, because just the other day, she...was a he. 
Shunned by the girl of his dreams, Hazumu loses himself in the mountains and is promptly squashed by an oncoming space ship. The alien inside, feeling guilty, rebuilds Hazumu's body...but as the wrong gender! 
Now Hazumu must learn how to be the girl his parents always wanted while dealing with the trials and tribulations of being caught in a love triangle between two girls--his childhood friend, Tomari, and Yasuna, the girl who rejected him but is now strangely attracted to him/her! 
(Source: Seven Seas Entertainment).

Namiko Tsuki